A study in Beijing, China of 112 pathologically confirmed epithelial ovarian cancer cases and 224 age-matched community controls enabled evaluation of risk in relation to reproductive, medical, familial, and selected lifestyle factors. An inverse relationship was observed between the number of full-term pregnancies and ovarian cancer risk. Compared to nulliparous women, subjects with one, two, or three full-term pregnancies were at 50%, 70%, or 90% reduced risks, respectively (P for trend less than 0.01). A positive correlation was found between the number of ovulatory years and risk, with a 2.6-fold increased risk for women with 30 or more compared to less than 10 ovulatory years (P for trend less than 0.01). Infertility, as estimated in various ways, was also found to be an important risk factor. When parity was taken into account, age at first pregnancy was not related to ovarian cancer risk. No protective effect was associated with mumps virus infection. In contrast, risk increased significantly as serum mumps virus antibody titres increased (P for trend less than 0.01). An elevated risk was found in women with a history of long-term (greater than 3 months) application of talc-containing dusting powder to the lower abdomen and perineum (Relative risk 3.9, 95% confidence interval: 0.9-10.63). These findings suggest that Chinese women have risk factors similar to those of occidental women.
PIP: Data for 112 patients with epithelial ovarian cancer were compared with data for 224 age-matched community controls from the metropolitan area of Beijing, China to determine the role of risk factors in a low incidence area (5/100,000 in Shanghai, China compared with 12.9 in San Francisco, California) and whether these factors vary with those found elsewhere. Women who experienced 1, 2, and 3 full-term pregnancies had a 50%, 70%, and 90% reduced risk of ovarian cancer (p.01). Late age at 1st pregnancy appeared to have a strong effect on ovarian cancer, but after adjusting for parity and education its effect disappeared. Married nulliparous women were 5.7 time more likely to develop ovarian cancer than single nulliparous women (p=.01). Moreover married women who tried to conceive for 12 months had a relative risk (RR) for ovarian cancer of 5.6 (p=.01). Women who had experienced =or+ 30 ovulatory years were 2.6 times more likely to develop ovarian cancer than those who only experienced 10 years (p.01). Cases had significantly higher mumps antibody titers than did the controls (RR=1.8 for antibody titer of 1: 20; RR=3.6 for 1: 40; p.01) indicating that a mumps virus infection does not have a protective effect against ovarian cancer as reported in another study. Women who had applied talc powder to the lower abdomen and perineum for 3 months were 3.9 times at risk than those who did not. Women who used oral contraceptives (OCs) for 1 year had a decreased risk of ovarian cancer (RR=.7) and those who took OCs for 1-2 years and 3 years had an elevated risk (RR=1.4 and 1.1, respectively), but the trend was not significant (p=.75). The risk factors of ovarian cancer for Chinese women were comparable to those of western women.